Method and apparatus for regulating heat flow in autoclaves

ABSTRACT

The invention relates to a method in autoclaves, the autoclave being divided into imaginary areas, the areas being heated by the feeding of steam into the areas in order to heat goods which have been placed in the autoclave so that it reaches sterilising temperature, whereby the feeding of heat between the areas is controlled. Such control is effected by successive registration of the temperatures in the areas and when the temperatures differ between the areas, the feeding of steam to the area which temporarily has a higher temperature is ceased, and as soon as the temperature in the adjacent area has passed the last mentioned temperature, the feeding of steam to that same area is resumed. In a device for the carrying out of the method, a temperature meter is arranged in each area. These meters are connected to a control unit, which is arranged to register the measured temperatures given by the meters and to control the function of the valves in the steam feeding pipes to the areas according to the method of the invention.

The invention relates to a method and a device in autoclaves, comprisinga container which is divided into imaginary areas, which are heated bythe feeding of steam into the areas in order to heat goods which havebeen placed in the autoclave so that said goods reach sterilisingtemperature.

For a long time, these kinds of autoclaves have been used whensterilising newly manufactured products which have to be sterilisedbefore being put on the market. Infusion solutions, such as glucose orblood plasma, or vitamins and proteins in solid or liquid state areexamples of such products.

After completed manufacture of a product of any of the above mentionedkinds, the product is loaded as goods onto carriages, the carriagesbeing placed in one area each in the autoclave, said autoclave willsubsequently be closed, and steam will be fed into each area in order tosterilise the goods.

The products are manufactured according to the market demand, usually invery different quantities depending on the product. A problem in thisconnection is that the demand for a product might be so small thatwithin a certain time one is able to fill one carriage only, whilst theautoclave is dimensioned for several carriages. Disregarding this factand leaving one or several areas in the autoclave empty during thesterilising process is however, most disadvantageous. Steam which is fedinto the empty area/areas will flow to the cool goods on the carriageand consequently the outermost goods will become more rapidly heatedthan the goods placed in the centre. Said goods may be of a nature thatdoes not allow exposure to too high temperatures during too longperiods. This would happen in the above mentioned case where theduration of the sterilising process is determined by a measuring probewhich is placed at the centre of the carriage. For thermolabile goods,such as sugar solutions (glucose), the reaching of high temperatures attoo early a stage would lead to caramelization, which in turn would leadto the goods having to be discarded. Thus, development of thesterilising process is achieved only when the interplay between heat andtime is correct.

Nor is it advisable to choose an alternative arrangement where, afterhaving loaded goods for sterilisation onto a carriage, the sterilisationof a product is postponed until sufficient quantities have been producedto fill the autoclave with carriages containing the same kind ofsterilising goods. Several kinds of products are so sensitive that theyhave to be discarded if they are not sterilised within a few hours ofthe manufacturing.

By means of the invention, a method, by which the above describedproblem can be solved has been provided by regulating the feeding ofsteam and consequently the feeding of heat into the different areas ofthe autoclave. The method is characterised in that upon registration inone area of a temperature which by a predetermined number of degreesexceeds the simultaneously registered temperature level in another area,preferably the adjacent area, the feeding of steam to thefirst-mentioned area will be interrupted and upon registration of atemperature in the same area which equals the level of, or is close tothe level of said other or adjacent area, steam will again be fed to thefirst-mentioned area.

The characteristic features of the device for carrying out the methodaccording to the invention are described in the appended claim 2.

The method and the device according to the invention will be describedin closer detail in the following with reference to the accompanyingdrawing, in which

FIG. 1 illustrates a longitudinal sectional view of an autoclave and

FIG. 2 illustrates a cross-section of the same autoclave.

The autoclave illustrated comprises a container 1, which has beendivided into three imaginary areas 4, 5 and 6 by dash-and-dot lines.From a steam source not illustrated a main pipe 7 feeds steam through amain valve 8 and three branches 9, 10, 11 and closing valves 12, 13 and14 respectively to the three areas 4, 5 and 6 in the container 1. In thedrawing, the charging hole 15 of the pipe 9 in the area 4 and thecharging hole 16 of the pipe 11 in the area 6 are the only onesillustrated. In the area 5 is placed a carriage 17 with goods 18thereon, in the example shown said goods consisting of bottlescontaining some kind of solution which is to be sterilised.

According to the invention, each area 4, 5, 6 has a temperature meter19, 20 and 21 respectively. These meters 19, 20, 21 are connected to acontrol unit 22, which is arranged to register the levels of temperaturemeasured by the meters.

In order to elucidate the invention and its function, an area 5 has beenillustrated in the drawing, which area has partly been filled withsterilising goods 18, while the remaining areas 4 and 6 are empty. Iftraditional technology is used, the steam is fed in equal quantitiesinto all areas 4, 5, 6, making the hot steam in the areas 4 and 6 flowtowards the goods 18 which in the initial stage is cool, and primarilyheat the outermost bottles on each side. These bottles will thus reachsterilising temperature earlier than the mid-section of the goods 18,where the sensing which decides the length of the sterilising time takesplace. The peripheral portions of the goods 18 will thus have too high atemperature during too long a period of time and consequently, if thegoods 18 is thermolabile, be destroyed.

According to the invention, the control unit 22 is arranged to controlthe function of the valves 12, 13, and 14 in such a way that when, inthe areas 4 or 6 wherein the temperature rises more quickly, saidcontrol unit registers a temperature which reaches a predeterminedlevel, which is, for example 5° C., higher than the temperaturesimultaneously registered in the area 5, the control unit makes thevalve 12 and/or the valve 14 cut off the feeding of steam to the area 4and/or 6. When a temperature is registered in these areas 4 and 6equalling that of, or close to the temperature of the mid-area 5, where,meanwhile, the temperature is rising, the control unit 22 is arranged tomake the valve 12 and/or the valve 14 to open its corresponding pipe 9,11 whereby steam will again be fed into the area 4 and/or 6. Due to theregulation by the control unit during the entire development of thesterilising process, the feeding of heat to the sterilising goods 18will be automatically adjusted in relation to time, thus ensuring thatthe development of the sterilising process is carried out in a correctway.

The method and the device according to the invention facilitates theentire process. Hence, an operator can arbitrarily place one carriage 17in each area 4, 5, 6 in the autoclave or in one or two of these areasonly. In the case where only one carriage 17 with goods 18 is to beplaced in the autoclave the operator need not consider into which area4, 5, 6 to place this carriage 17, but instead, the operator canarbitrarily place the carriage in any of the areas.

The invention is not limited to the illustrated and described embodimentbut can of course be varied in several ways within the scope of theappended claims. Hence, the invention may also be used in an autoclavewhich is divided into two areas or into a much larger number of areasthan illustrated, and into which autoclave several carriages 17 arepositioned, while simultaneously, several areas are empty.

What is claimed is:
 1. A method for regulating the flow of heat between areas in an autoclave, comprising: placing goods to be sterilized in a container of the autoclave, the container having a plurality of areas; heating the container by feeding steam into the areas in order to heat the goods so that the goods reach a sterilizing temperature; regulating feeding of steam to the container such that, upon registration in a first area of the plurality of areas of a temperature level which exceeds by a predetermined number of degrees a simultaneously registered temperature level in a second area of the plurality of areas, feeding of steam to the first area is interrupted and, upon registration of a temperature level in the first area which substantially equals a temperature level of the second area, steam is fed to the first area.
 2. A heat regulating autoclave arrangement, comprising: a container into which goods to be sterilized are adapted to be placed; a plurality of pipes connected to the container; a plurality of valves corresponding to the plurality of pipes, each pipe having a valve, wherein steam is adapted to be delivered to a plurality of different areas of the container through the pipes for heating the goods to a sterilizing temperature; a plurality of temperature meters arranged in each of the different areas of the container; a control unit arranged to receive signals from the plurality of temperature meters, to register temperature levels in the different areas measured by the temperature meters, and to control the valves such that, upon registration in a first area of the different areas of a temperature level which exceeds, by a predetermined number of degrees, a temperature level in a second area, a valve on a pipe to the first area is closed to cut off steam to the first area and, upon registration of a temperature level in the first area of substantially the same temperature level of the second area the valve on the pipe to the first area is opened to permit a flow of steam into the first area. 